Atrial Septal Defect
An atrial septal defect (ASD) is a hole in the part of the septum that separates the atria (the upper chambers of the heart). This hole allows oxygen-rich blood from the left atrium to flow into the right atrium instead of flowing into the left ventricle as it should. This means that oxygen-rich blood gets pumped back to the lungs, where it has just been, instead of going to the body.
An ASD can be small or large. Small ASDs allow only a little blood to flow from one atrium to the other. Small ASDs don’t affect the way the heart works and don’t need any special treatment. Many small ASDs close on their own as the heart grows during childhood.
Medium to large ASDs allow more blood to leak from one atrium to the other, and they’re less likely to close on their own. Most children who have ASDs have no symptoms, even if they have large ASDs.
How normal heart works?
The normal human heart is responsible for efficiently receiving and pumping blood. Proper blood flow is vital to health because the body’s tissues rely on the blood to carry nourishment (oxygen, glucose) and remove waste products (carbon dioxide). Under normal conditions, the cardiovascular system (heart, blood vessels) contains two separate circulatory systems – venous (right) and arterial (left). Venous (deoxygenated, blue) blood returns from the body to the right atrium.
Blood flows from the right atrium through the tricuspid valve into the right ventricle where blood is actively pumped across the pulmonary valve and into the pulmonary arteries. The main pulmonary artery divides into large right and left pulmonary arteries and then to small pulmonary arterioles. Adjacent to the small arterioles, numerous pulmonary air filled sacs. Within these small sacs, gases are exchanged. Waste products from the venous blood enter the air sacs and are removed from the pulmonary system when we breathe out (exhale). Oxygen that enters the lungs when we breathe in (inspiration) enters the small air sacs and diffuses into the blood. Oxygen-rich (red) blood returns from the lungs via pulmonary veins to the left atrium.
Muscular and connective tissues separate the right (blue blood) from the left (red blood) side of the heart. The heart is separated at the level of the receiving chambers (right and left atria) by the atrial septum, and at the pumping chambers (right and left ventricles) by the ventricular septum. Persistent opening between the atrial and ventricular septa in postnatal life is abnormal.
Types –
The four major types of ASDs are:
• Secundum.
This defect is in the middle of the atrial septum. It’s the most common form of ASD. About 8 out of every 10 babies born with ASDs have secundum defects. At least half of all secundum ASDs close on their own. However, this is less likely if the defect is large.
• Primum.
This defect is in the lower part of the atrial septum. It often occurs along with problems in the heart valves that connect the upper and lower heart chambers. Primum defects aren’t very common, and they don’t close on their own.
• Sinus venosus.
This defect is in the upper part of the atrial septum, near where a large vein (the superior vena cava) brings oxygen-poor blood from the upper body to the right atrium.
• Coronary sinus
It occur when there is a defect in the wall between the coronary sinus and the left atrium. This is the rarest type of atrial septal defect and affects the blood flow from the heart’s own vein.
Symptoms –
ASD signs and symptoms in babies include:
• Shortness/gasping of breath
• Swelling of legs, feet or abdomen
• Heart palpitations or skipped beats
• Frequent lung infections
• Heart murmurs (Most common)
Causes –
Although doctors know that this type of a heart defect is present at birth, there is no definite cause. What is known is that, congenital heart defects appear to run in families and sometimes occur with other genetic problems, such as Down syndrome.
Risk Factors –
Some of the possible factors that may increase the risk of having a baby with a heart defect. They include the following:
• Rubella infection-
German measles during the first few months of pregnancy can increase the risk of fetal heart defects.
• Drugs, tobacco, smoking and alcohol-
Use of certain medications, tobacco, alcohol or drugs, such as cocaine, during pregnancy can harm the developing fetus.
• Obesity-
Being extremely overweight may also play a role in increasing the risk of having a baby with a birth defect.
• Phenylketonuria (PKU)-
PKU patients not following the PKU meal plan, may be more likely to have babies with heart defects.
Complications –
A small atrial septal defect might never cause any concern. Small atrial septal defects often close during infancy.
Larger atrial septal defects can cause serious complications, including:
• Right-sided heart failure
• Irregular heartbeats (arrhythmias)
• Stroke
• Early death
• High blood pressure in the lung arteries (pulmonary hypertension)
Pulmonary hypertension can cause permanent lung damage. This complication, called Eisenmenger syndrome, usually develops over many years and occurs uncommonly in people with large atrial septal defects.
Diagnosis –
Some atrial septal defects are diagnosed before or soon after a child is born. However, smaller atrial septal defects may not be diagnosed until later in life.
If an atrial septal defect is present, the health care provider may hear a whooshing sound (heart murmur) when listening to the heart with a stethoscope.
Tests that are done to help diagnose an atrial septal defect include:
• Echocardiogram.
This is the most commonly used test to diagnose an atrial septal defect. Sound waves are used to create pictures of the heart in motion. An echocardiogram can show how well blood is moving through the heart and heart valves.
• Chest X-ray.
A chest X-ray shows the condition of the heart and lungs.
• Electrocardiogram (ECG or EKG).
This quick and painless test records the electrical activity of the heart. An ECG can help identify irregular heartbeats (arrhythmias).
• Cardiac magnetic resonance imaging (MRI) scan.
This imaging test uses magnetic fields and radio waves to create detailed images of the heart. A health care provider might request this type of MRI if echocardiography didn’t provide a definitive diagnosis.
• Computed tomography (CT) scan.
This uses a series of X-rays to create detailed images of your heart. It can be used to diagnose an atrial septal defect and related congenital heart defects if echocardiography hasn’t definitely diagnosed an atrial septal defect.
Treatment –
Treatment will depend on your child’s symptoms, age, and general health. It will also depend on how severe the condition is. Once an atrial septal defect is diagnosed, your child’s cardiologist will check to see if the defect is closing on its own. A secundum atrial septal defect, the most common type of atrial septal defect, often closes on its own as your child grows.
Treatment may include:
• Medicine.
Many children have no symptoms and don’t need medicine. But medicine can help some children’s hearts work better. For example, diuretics (water pills) help the kidneys get rid of extra fluid from the body, which may occur when the heart is not functioning properly.
• Surgery.
An atrial septal defect will often be corrected with surgery if it has not closed by the time a child starts school or if the hole in the heart is large. The surgery is done under general anesthesia and the hole in the heart is closed with stitches or a special patch. After the surgery, your child’s doctor may prescribe antibiotics to prevent bacterial endocarditis, an infection of the lining of the heart.
• Device closure.
During a cardiac catheterization, a special device called a septal occlude is put into the atrial septal defect. The septal occlude device stops blood from flowing through the hole in the heart.
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